New York City sanitation officials are warning travelers of potentially hard-to-see black ice that could emerge early Friday morning, as droves of people are expected to hit the road ahead of a frigid holiday weekend.

A heavy storm could dump as much as 2 inches of rain in the New York City area on Thursday and into Friday, but then temperatures are expected to plummet well below freeing within hours, Friday morning. The city Department of Sanitation will mount what it has characterized as an aggressive campaign to salt city roads, issuing a winter operations advisory that goes into effect Friday at 8 a.m.

The department’s fleet of more than 700 salt spreaders will blanket the five boroughs as temperatures drop in an effort to ensure streets and bike lanes are safe enough to remain open.

“People can get where they need to go, but I want New Yorkers to know that every single street is on one of our routes and every route will be assigned,” Sanitation Commissioner Jessica Tisch said in an interview with Gothamist on Thursday. “That said, we do want anyone able to stay home or take public transit to do so.”

Though snow is possible, it’s not likely to accumulate heavily on roadways. Plowing is unlikely, according to the department. Thin, barely visible layers of ice on the roadways known as black ice, however, are a possibility — particularly in the event of a flash freeze.

“Black ice can make for dangerous driving conditions and fewer cars on the road make it easier for our crews to do their jobs,” Tisch said.

Other agencies are also taking precautions. The transportation department will pause its Open Restaurants program for outdoor dining from 8 p.m. Thursday until the same time Friday night.

Tisch said residents can anticipate “a white Christmas” this year, though the roads won’t be covered in snow: “It will be salt."